Group Messages from iPhone

I am the only one out of a group of friends that doesn't have an iPhone. Whenever they send a group message out i receive it as a multimedia message and can not reply as a group. Does anyone know an app or something that will allow me to see group messages and reply to all?

The instructions are a little muddled, but might be a partial solution

Specifically, once you set them up as a group, and you select that group there are two icons at the bottom of the screen... the index card one that lets you add more people to the group... the second is the 3-prong arrow... if you click on that you can send messages or emails to that group.